Semiconductor processing in the fabrication of integrated circuitry typically includes the deposition of layers on semiconductor substrates. One such method is atomic layer deposition (ALD), which involves the deposition of successive monolayers over a substrate within a deposition chamber, typically maintained at subatmospheric pressure. With typical ALD, successive mono-atomic layers are adsorbed to a substrate and/or reacted with the outer layer on the substrate, typically by the successive feeding of one or more deposition precursors to the substrate surface.
By way of example only, an exemplary ALD method includes feeding a single vaporized precursor to a deposition chamber effective to form a first monolayer over a substrate received therein. Thereafter, the flow of the first deposition precursor is ceased and an inert purge gas is flowed through the chamber effective to remove any remaining first precursor that is not adhering to the substrate from the chamber. Alternately, perhaps no purge gas is utilized. Subsequently, a second vapor deposition precursor, the same or different from the first precursor, is flowed to the chamber effective to form a second monolayer on or with the first monolayer. The second monolayer might react with the first monolayer. Additional precursor flows can form successive monolayers, or the above process can be repeated until a desired thickness and composition layer has been formed over the substrate.
Exemplary types of materials deposited by ALD include metals and metal compounds. Common precursors used in depositing metal and metal compounds by ALD include metal halides, for example TiCl4. A typical intent in ALD involving such a metal halide is to flow TiCl4 to the substrate, preferably causing TiClx to chemisorb to available bonding sites on a substrate, with one or more chlorine atoms being a by-product either as chlorine atoms or chlorine gas (Cl2) as an effluent. The remaining TiClx will be positively charged, and provide an available bonding site for subsequent monolayer formation thereon or therewith. If elemental titanium is the desired layer to be deposited, subsequent flowing of TiCl4 can desirably replace the Clx with TiClx thereby creating Ti-TiClx bonds. Subsequent TiCl4 precursor flows can desirably result in an increasing thickness/growing elemental Ti layer. Alternately by way of example only, alternating TiCl4 and NH3 flows can be utilized to form TiN.
Regardless, a perfectly saturated monolayer of the TiClx moiety is typically not the result. Further and accordingly, otherwise available TiClx bonding sites might be occupied by chlorine atoms. Further and regardless, not all of the chlorine atoms of the TiClx monolayers will necessarily be removed from the layer, thereby undesirably resulting in some chlorine incorporation in the layer being formed. Accordingly, it would be desirable to reduce the incorporation of chlorine or other halogens in deposited layers utilizing metal halides as deposition precursors.
While the invention was motivated in addressing the above identified issues, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.